Pituitary adenomas removed during surgery will be evaluated for immunoreactive growth hormone and prolactin content, for correlation of clinical and histophysiological data, at the light- and electron- microscopic level. Phosphodiesterase in normal and goitrous thyroids will be compared, with emphasis on the possibility that the enzyme in goiters, as was found for adenylate cyclase and protein kinase, may show qualitative differences from its normal counterpart. On the basis of the effects of thyrotropin, mononitrotyrosine, propylthiouracil and perchlorate on rat thyroid iodide content (determined by gel electrophoresis), a model of thyroid iodide origins, turnover and fate will be evolved.